The optical properties of a particular pair of eyeglasses are fixed at the time of manufacture. The needs of the owner of the eyeglasses with respect to vision correction or vision modification vary under different conditions. For example, reduction of light intensity as provided by sunglasses is desirable at certain times and locations but not at others. In some situations, such as where a person is operating a computer, a temporary increase in magnification can be helpful. Wearing of yellow tinted glasses can aid night vision but this may not be desirable during the daytime or in the presence of indoor lighting.
Obtaining two or more pairs of eyeglasses for use under different conditions is costly particularly in the case of prescription eyeglasses that are fabricated to meet the specialized needs of the particular person. It is simpler and more economical to make use of attachments of the type that can be temporarily clipped onto the person's basic vision correcting eyeglasses at times when reduced light intensity or some other vision modification is needed.
Prior clip-on eyeglass accessories of this kind have not been entirely satisfactory for several reasons.
For example, eyeglasses are made in a variety of sizes and a variety of configurations. Further, the configuration of eyeglasses tends to vary from time to time because of changes in fashion or for other reasons. Many prior clip-on accessories are mass produced in one size and shape or a limited number of sizes and shapes. Consequently the optical elements of such accessories often do not have the same configuration and spacing as the lenses of the eyeglasses with which they are used. This discomformity can cause several problems. Undersized optical elements and optical elements that are out of register with the eyeglass lenses tend to disrupt the wearer's field of view and also present an unesthetic appearance to others. Oversized optical elements may contact the wearer's skin in an irritating manner and have projecting edges that may promote dislodgement of the accessory from the eyeglasses.
In order to alleviate these problems, some manufacturers of eyeglass frames provide clip-on sunglass accessories having optical elements that conform with the lenses and lens spacings of a particular frame. Prior conforming clip-on accessories of this kind are largely limited to use with the specific frame configuration for which the accessory was designed or at best are suitable for use with a limited number of frames that have closely similar configurations. Dispensing opticians typically offer a variety of different frame styles and stocking of a corresponding large inventory of different clip-on accessories is costly and an operational complication. As a practical matter, such conformed clip-on accessories may not be available for many models of eyeglass frame.
The prior conformed clip-on accessories also have a costly construction which relies on rims on the optical elements to interconnect and secure the other components of the accessory such as a bridge member and clasps for engaging the eyeglasses.
The present invention is directed to overcoming one or more of the problems discussed above.